NASA’s seven astronauts aboard the space shuttle Atlantis are circling the Earth as we speak, but an attentive listener may find their chats with Mission Control confusing.

That’s because nearly every one of Atlantis’ seven STS-117 astronauts has their own unique call sign - or nickname - of choice. So rather than Rick, Lee, Patrick, Steven, John, Jim and Clayton, they are: CJ, BRU, Swanny, Danny, JR and Clay.

Some of their monikers have a straightforward abbreviation: mission specialists Steven “Swanny” Swanson and Jim “JR” Reilly II (he’s also a ‘junior’ apparently), for example,  or Patrick “Pat” Forrester and Clayton “Clay” Anderson. John Olivas, meanwhile goes by “Danny” and I can’t believe it’s not related to that middle initial ‘D.’ in his NASA bio.

But Atlantis commander Rick Sturckow and pilot Lee Archambault carry call signs left over from their military days in the U.S. Marine Corps and Air Force, respectively.

Sturckow’s “CJ” nickname is an abbreviation for Caustic Junior and stems from his apparent resemblance to a former superior officer whose own moniker was simply “Caustic”

Archambault’s handle BRU (pronounced “brew”) is rooted in bad luck.

“I had an unfortunate experience with a Bomb Rack Unit on an F-111 jet,” the Atlantis shuttle pilot explained before launch. Unfortunate or not, the experience apparently made an impression.

So mystery solved. There’s a handy primer on the many monikers of NASA’s STS-117 astronauts. I hope it comes in handy over the next 11 days.